using System;

public class Program

{

    public static void Main()

    {

        int [] arr ={0,0,0,0,0,1,1,1,1};

        int mid;

        int left =0;

        int right=arr.Length;

        while(right>=left)

        {

            mid=(right+left)/2;

            if(arr[mid]==0)

                if(arr[mid+1]==1)

                Console.WriteLine(mid);

                if(arr[mid]==1)

                right=mid-1;

                left=mid+1;

        }

        Console.WriteLine(-1);

    }}

​